1. Field of the Invention
The present invention relates to a method for manufacturing a liquid crystal display device applicable to: a portable data terminal to be viewed by a plurality of persons; a flat panel display such as a personal computer, a word processor, amusement equipment and television; and a display board, a window, a door or a wall, taking advantage of a shutter effect.
2. Description of the Related Art
Japanese Laid-Open Patent Publication Nos. 6-301015 and 7-120728 disclose a liquid crystal display device including a liquid crystal region surrounded by a polymer region, with excellent mechanical strength and viewing angle characteristics, and a method for manufacturing such a liquid crystal display device.
FIG. 12 is a schematic partial cross-sectional view of a liquid crystal display device 100 disclosed in Japanese Laid-Open Patent Publication No. 6-301015. In the liquid crystal display device 100, a liquid crystal layer 27 sandwiched between a pair of substrates 21 and 23 includes a polymer region 28 and a liquid crystal region 29 substantially surrounded by the polymer region 28. The liquid crystal region 29 is formed so as to correspond to a pixel defined by electrodes 22 and 24 facing each other. Liquid crystal molecules (not shown) in the liquid crystal region 29 are axisymmetrically aligned about a central axis (perpendicular to the substrates) of the liquid crystal region 29 in a radial manner or a concentric (tangential) manner. As a result, the liquid crystal display device 100 has wide viewing angle characteristics.
The liquid crystal display device described above is fabricated as follows. A precursor mixture containing a liquid crystal material, a polymerizable resin, and a polymerization initiator is interposed between a pair of substrates. Then, the precursor mixture is irradiated with light while regulating an irradiation intensity through a photomask, or the like, so as to cure the polymerizable resin material. As a result, a liquid crystal region is formed that is substantially surrounded by a polymer region formed of a polymer material obtained from the polymerizable resin material. The resultant liquid crystal display device has excellent mechanical strength and viewing characteristics because the polymer material serves to keep a distance between the pair of substrates along with the spacer and the sealing agent and because liquid crystal molecules in the liquid crystal region surrounded by the polymer material are not unidirectionally but multidirectionally orientated.
However, the conventional liquid crystal display device described above is disadvantageous in that T.sub.NI (phase transition temperature between Nematic phase and Isotropic phase) of a liquid crystal material within the liquid crystal region is lowered, a transmittance is lowered, a threshold voltage is increased, a response speed is low (i.e., response time is long) or the like. Furthermore, a disclination line appears in the peripheral region within the liquid crystal region.